Device for minimizing the effects of torsion when reproducing a magnetic record wire



March 25, 1952 AN 2,590,627

DEVICE FOR MINIMIZING THE EFFECTS OF TORSION 7 WHEN REPRODUCING A MAGNETIC RECORD WIRE Filed April 29, 1948 3.5 Amp/z/xler Fig. 6. /3.B| 5/b 5/ Fig: 4.

. My 3e 9 1/07 5 \vad v5- WITNESSES: v3 INVENTOR fl 25' Bernard 5'. Lena/van.

4 flfM? ATTO R N EY Patented Mar. 25, 1952 ,-DEYICE :FOR 'MINIMIZING .THE EFFECTS OF TORSION WHEN REPRODUGING A MAG- ,NETIC RECORD WIRE -Bernard E. Len'ehan, Bloomfield, N. J., assignor to Watinghouse Electric Corporation, East Pittsburgh, 2a., a :corporation of Pennsylvania 'ber.

Application Apiil29, 1948, Serial No. 24,038

6 Claims. 1 jI'his invention relates to the reproduction of signals ,andit has particular relation to the -reproduction-of a magnetic signal "transversely disposed in an elongated magnetic member 'or wire.

In accordance ,with "the invention, a--pair of tion ,of its axis.

travel past'the pickups.

her.

'tions of a variable angle, wherein a system is provided for changing the time phase of the signal components relative to each other and adding the resulting components to provide a resultant signal which is independent of the aforesaid angle.

It is also an object of the invention to provide an improved method for reproducing a transverse'signal carried by an elongated member.

junction with the accompanying drawing, in

which:

Figure 1 is aview-in side 'elevation-withparts Alter- A coil '50 .5 pickups is disposed adjacent ajpoint'on-the path broken away of a prior art system for magoftravel'ofan elongated memberihaving a signal netically recording and reproducing signals, transversely carried thereby. The elongated Fig/2 is a view in perspective withparts-br'oken member may be in the form of 'a magnetic -wire away showing a modified structure for maswhich is mounted for movement in the direcneticallyrecording and'reproducing signals,

The two pickups are disposed Fig.3 isaschematic viewwithparts-inperspecv.at,an angle :relative to each other about the "axis tive and parts broken away of asignal-reproducofthe wire. The signal components derived'from mg system embodyin the invention, thepickups'are shifted intimephaserelative to Figs. 4, 5, 6 and 7 are vector diagrams showeach otherthrough'an angle substantially'equal l5 ing vector relationships present in the system to thespace angle'between the pickups, andthe of Fig. 3, and phase-shifted components are added to provide "Fig. 8 is a view in elevation of amodified pickup va resultant signal which "is substantially inde head which may be employed in the system "of pendent .ofqthe orientation of thewire during'it's Fig. 3. .20 Referring to the drawing, Fig. 1 shows an'elon-- jIt is, therefore, an object of the invention to gated member I which ismounted'for movement provide an improved system jfOl reproducing a in the direction of its length, as shown by an transverse signal carried by an elongated memarrow 3, past the poles of an electromagnet "5. The elongated member I may vary appreciably It isaiurther object of the inventionto proin composition and structure. 'It may take the vide asystem'for reproducing a transverse signal form of a ribbon having a rectangularcros's seccarried by an elongated member mounted for tion. Alternatively the elongated member I may movement in the direction ofits length, wherein represent a round or oval wire. If desired, the a pair of pickups is located adjacent the path member I may be constructed of a material or of travel of the member and are angularly Ldisno alloy having hard magnetic properties. placed about the path of travel to produce outnatively, the member I may have a non-magnetic puts or signal components 'in time phase with core, such as a brass, paper or plastic core, which the signal but having magnitudes varying as carries a layer or coating of hard magnetic -rna functions of the orientation of the member with terial. Such members which are capable of r'erespect to the pickups and wherein a combiner ceiving and storing a magnetic record are well is included for shifting the phases of the comknown in the art. ponents relative to eachother and adding the The electroma'gnet 5 is illustrated as comprisshifted components for producing a resultant ing a soft magnetic ring-shaped core 50. which signal for application to translating means hav has a gap 5?) defining pole pieces located adjacent ing a magnitude which is substantially inde- 4n the path of travel of the member I. pendent of the orientation of the elongated memsurrounds a portion of the core 5a.

, When an alternating signal which, for ex- It is a still further object of the invention to ample, may represent speech, is applied to "the provide a combiner for two in-phase signal comcoil 50 (a hig q y alte at n -Cu re t ponents having magnitudes which vary as funcbias also may be simultaneously applied to the coil in accordance with conventional practive), the member I in its travel past the electromagnct 5 is magnetized to store the signal therein. The direction of the magnetic field in the member 5 is substantially parallel to the axis of the member, as indicated by the arrows I.

In order to reproduce the signal stored in the member l, the member again may be guided in the same direction past the electromagnet 5. If the coil 50 is connected through a suitable amplifier to translating means such as a loud speaker, the speech recorded in the wire is reproduced by the loud speaker.

It should be noted that the reproduction of the signal is independent of the orientation of the member I about its path of travel. Regardless of the rotation of the member I about its axis, the signal stored therein remains substantially parallel to the axis of the member. Consequently, the system of reproduction represented in Fig. 1 may be employed for substantially any shape in cross section of the member I. It should be noted that the plane of the electromagnet in Fig. 1 is parallel to the axis or path of travel of the member I.

In Fig. 2, the member I is shown located between the pole faces of the electromagnet 5. The electromagnet 5 now is in a plane substantially transverse to the axis or length of the member I. When a signal is applied to the coil 50, a magnetic field as represented by the arrows 9 is produced in the magnetic member I which is substantially transverse to the axis or length of the member I. Consequently, the signal may be said to be transversely stored in the magnetic member I.

When the signal stored in the member I of Fig. 2 isto be reproduced, it again may be passed in the same direction represented by the arrow 3 between the pole faces of the electromagnet 5.

,If the orientation of the magnetic member I remains similar to that prevailing during the recording operation, a loud speaker connected through an amplifier to the coil 50 will reproduce the signal or speech stored in the member I. However, if the orientation of the member I should change, the signal may not be satisfactorily reproduced.

Let it be assumed that during its travel between the pole faces of the electromagnet 5 during a reproducing operation,-the member I together with the signals stored therein is rotated 90 from the position illustrated in Fig. 2. Under such circumstances, the direction of the arrows 9 which now represent the stored signal is parallel to the pole faces of the electromagnet 5 and the coil 5c is completely deenergized.

If the'magnetic member I is a round wire such as the 4 mil or, 6 mil wire commonly employed in magnetic sound recorders and reproducers, it

is impracticable to maintain a desired orientation'of the wire during its movement adjacent the associated pickup. For this reason when transverse recording and reproduction have been employed in the prior art in the manner discussed with reference to Fig. 2, it has been the practice to employ a magnetic member in a form of a tape or ribbon which can be maintained in the desired orientation during both recording and reproduction operations.

In accordance with the invention, a signal transversely disposed in the member I is satisfactorily reproduced. As shown in Fig. 3, a pair of pickups II and I 3 is disclosed which include magnetic cores Ila and I3a having associated therewith, respectively, coils IIb and I31). These pickups II and I3 are disposed adjacent a predetermined point in the path of travel of the member I but are displaced angularly relative to each other about the axis or path of travel of the member I. Preferably, the angle of displacement is 90 but some variation in the angle is permissible with reasonably satisfactory results.

The pickups II and I3 may be similar to that illustrated in Fig. 2. However, in Fig. 3, the

4 pickups I I and I3 are shown having cores whit-3h are in the shape of rods extending from the member I for a distance 'suiiicient that the magnetic fields adjacent the remote ends of the cores are substantially uniform. The pole faces of the cores adjacent the member I have a diameter or size which is dictated in part by the size or diameter of the magnetic member I. When two cores are employed, as illustrated in Fig. 3, knots or splices in the member I pass readily thereover.

It will be understood that the member I in Fig. 3 is moved in the direction of its length or axis as represented by the arrow 3 at a uniform rate. Mechanism for this purpose is well known in the art andis represented in Fig. 3 by a capstan or pulley I5 which is rotated uniformly for the purpose of advancing the member I. As one example of a prior art "wire recorder reference may be made to Patent 2,351,005, issued June 13, 1944. I

The voltages or signal components induced in the coils IIb and I3b depend on the orientation of the member. I adjacent the pickups. Let it be assumed that the axes of the cores I'Ia' and I3a fall along the lines IIdand ISd'of'Fig. 4. These lines are perpendicular to each other. Let. the direction of the vector S in Fig. 4 represent at some instant the direction of magnetism of the signal stored in the member I at afpoint adjacent the pickups II and I3. In. Fig.4, this direction is such that the vector or signal S isdisplaced by a space angle 0. from the line IId. Under these circumstances the magnitudes of the components of the signal S effective for inducing voltages in the coils I Ib and IN) may be represented by vectors He and I3e.

It should be understood clearlythat the vectors IIe, I3e and S are all in time phase with each other. The vector diagram of ,Fig. 4 isia space diagram wherein the vectorsindicate'the direction in space of the signal S and the components He and I3e of the signal which are effective for inducing voltages in the pickup coils.

By inspection of Fig. 4, it will be observedthat the magnitudes of the voltages induced in'the coils IIb and I3b depend on the angle B'or on the orientation of the signal S with respect to the pickups. The vector IIe isequal to S'co'sine 0 (or S cos 6) whereasthe vector I36 is equal to SSinHOrSsinO).

The sum of these two quantities (S cosfl-I-S sin 0), is dependent on the value of the angle '0. Consequently, the resultant'signal obtained by the. direct addition of the outputs of the pickup coils II b and I312 would not provide a directly useful resultant signal representative of the signal stored in the member I. Sucha resultant signal would have a magnitude which varies with the orientation of the member I about its axis or path of travel adjacent the pickups.

In order to obtain a directly useful resultant signal, one of the signal components from the pickups is shifted in time phase relative to the remaining signal component through an. angle substantially equal to the space. angle between the pickups. To this end, the signal components derived from the pickup coils I I1) and I3b are applied, respectively, through amplifiers I1 and I9 and transformers 2| and.2 3 to a combiner 25. In order to facilitate adjustment of the balance between the signal components applied .to the combiner, the secondary windings of the transformers 2| and 23 maybe connected in series across a resistor 21. This resistor has an .adjustable tap 29 connected to the common lead .3! extending between terminals of the secondary By manipulation of the tap '29 the pr portion :of the resistor 2] connected across cc o the sec ar win in s may e d u te for thebest condition of balance.

I he m t u s of the t a iormer Z1 an 3 comprise two signal components which are always in time phase agreement or time phase o siti n- QWW t ma n tu 9? th c ii nent' a e de end nt o t or en at n o thememberl about its axis or pathof travel ad; jacent the pickups ll'a'nd l3.

" The output of the transformer 2| is connected across a resistor RI which may have a resistor R2 connected in series therewith. The voltage drop across the resistor 'Rl'is in phase with the current traversing the resistor and with the volta'ge across the secondary winding of the trans former 2|. 7

The desired phase shift is effected by shifting thephase of the output of the transformer 23 through an angle of substantially 90."I'o'this end a series circuit is connected across the secondary winding of the transformer 23 through conductors 33 and 35 which includes a capacitor Ql. It will be understood that the Voltage across the capacitor lags the current therethrough by an angle of 90. However, this voltage has a magnitude which is dependent on frequency. If a signal of only one frequency were stored in the member I, the capacitor Cl alone might suffice in the combiner to produce the desired phase shift. However, in order to permit utilization of the combiner with signals having a substan-,

tial range of frequency, such as a range" suitable for speech, an inductance coil Ll is connected in the series circuit includii'cgthe capacitor CI. Further improvement may be obtained by including a resistor R3 in this series circuit.

' The inductance coil LI has mutually coupled thereto a second inductance coil L2. The inductance coil L2 is connected in series with the capacitor Cl and the resistor RI across the output conductors 31 and 39 of the combiner.

The coil L2 has induced therein avoltage which is substantially in phase with the voltage across the capacitor CI but which varies oppositely in magnitude in response to a change in frequency of the input to the combiner. Consequently, the

magnitude of the resultant output of the capacitor Cl and the inductance coil L2 in series may be made substantially independent of frequency over .a substantial range.

Conveniently, the capacitor Cl and the inductance introduced by the coil Ll across the secondary winding of the transformer 23 may be resonated to a frequency which is substantially the geometric mean of the frequency range for which the combiner is designed. As the frequency deviates from the geometric mean, the magnitude of the voltage output of the capacitor C1 and the inductance coil L2 in series may change somewhat. If this change is objectionable, it may be substantially eliminated over the desired range by means of .a parallel resonant circuit comprising a capacitor C2 and an inductance coil L3.

This parallel resonant circuit is connected between the conductor 39 and the conductor 4! which extends from the upper terminals of the resistor to the upper terminal of the secondary winding of the transformer .2.I as vi ed Fig. The parallel resonant ci it is s ated to freouen wb ch fis' the eometric means of the .fifi.

ca nd 1y, at this frequency the parallel resonant circ itnmws "subs an ial n Curren "AS the re u nc deviates m th lse me r i ean t para lel resonan c r ui draws ur ent through the capacitorCi and the inductance coil L2' to produce an auxiliar'y'voltag'e drop which co e sates for e v ia i n n ma nitude which otherwise would result from a change' in frequency.

It will be noted that the resistors R2 and R3 substantially balance the input circuits to the combiner from the standpoint of resistance. A substantially complete balance may be and pref- 'er'ably is provided by including'a" parallel freso nant circuit comprising a capacitorIC3 and an inductance coil L4 connected across the secondary wi nding of the transformer 23. Thetwo'parallel resonant circuits may be of similar construction. As representative of suitable rallies Ifonthe components of the combiner, the following val es have been found suitable for a co iner designed for a frequency range of 150 to '5i00 0"cycles per second. This is adequate for transmission cf speech signals.

Mutual inductance between coils LI and L2=.0c

' henries. The coils may have a Q of 18' measured a at 1000 cycles per second.

The output conductors 31 and 39 of the cornbiner may be connected to suitable translat "g means 43, thety'pe of which depends onitih e nature of the signal stored in themember I. If the signal stored in the member I represents speech, the translating device 43'may be a transducer such as a loud speaker which reconnecta to the output of a suitable amplifier "'45. The input to the amplifier is derived from the conductors 37 and 39. "'Th e'o'p'eration of the combiner may be censidered by assuming first that an" altei natin'g signal stored in the member [is rpiesentedby the conventional expression A sinwt'wh ein 'A is a constant, a: is the frequency of the signal multiplied by 25%, and it represents time;

' It will be recalled that the outputsof the pickup coils Nb and l3b are related to'the stored I signal in accordance with "the expressionsfcost acres-s the resistor'Ri "of the combiner is represented the expression A cos 0 sin wt. It may be "assumed further that the voltage applied across the capacitor Cl and the coil 'Lf in series is represented by the expression 'A sin "0 sin wt.

. Theisum these two expressions would give a .S'=A cos 0 sin wt+A sin 0 sin t (1,)

th a le )0 o on the enta on o th member It s ide tofina t e m n t de o hes eenden q he tan e wa t fm 6 E'ouation l'is rotated in time phase throu h an abe -e t st? ease t he ens i w e the pickups or 90. This is effected by employing the voltage across the capacitor Cl and the coil L2 in series which under the assumed conditions has a value equal to A sin cos wt. Consequently, the sum of the voltages across the resistor RI, the capacitor Cl and the coil L2 which is applied across the conductors 3'! and 39 represents a resultant signal Rs=A cos 0 sin wt-i-zi sin I I tees wizA sin (ot+ii (2) inspection re ean that the maenitudesr there 'siiltar'it s gnarris is independent or th angle 1? or the ori ntat on of the m mber I. The effect cf the a'rigle t is to contriilthe phasefof the sie: nal. Changes in the orientation of the member I under the usual conditions encountered in re "careers and r'eproducers occur very slowly. Goriset u'ently, changes in phase represented were an le 9 ih Equation 2 have substantially no efiect 6n the output of the transducer 43; I

"me operation of the combiner also may b considered with reference to Figs. 5, 6 and 7 Let it be assumed first in Fig. that the orientation 6f the member I is such that the secondary voltages 6f the transformers 2| and 23 are represented by two vectors VI and V2 which are in time phase agreement and which are equal in magnitude. The effect of the combiner is to shift the phase of the vector V2 through an angle or 90 to provide a vector V3 which is added vectorially to the vector VI to provide the resultant signal RS. c

In Fig. 6 it is assumed that the orientation of the member 1 carrying the same signal is such that the outputs of the transformers 2| and 23 are re resented by the vectors V3 and V4 which are equal in magnitude but opposed in time phase. The combiner again shifts the phase of the vector V4 through an angle of 90 to provide a vector V5 which is added vectorially to the vector V3 to provide the resultant signal RS.

Finally, in Fig; 7 the orientation of the member 1 carrying the same signal is assumed to be such that the outputs of the transformer 2| and 23 are represented by the vectors V6 and V1 which are in time phase agreement but which are substantially different in magnitude. The combiner shifts the phase of the vector V1 to provide a vector V8 lagging the vector V! by 90. The vectors V6 and V8 add vectorially to provide the resultant signal RS".

All of the resultant signals RS, RS and RS" are equal in magnitude but displaced in time phase from each other. Since the transducer is responsive substantially only to the magnitude of the resultant signal, the orientation of the member I has substantially no effect on the output of the transducer. As previously pointed out, the changes in phase encountered in conventional recorder and reproducer magnetic members is extremely gradual and slow.

The pickups H and 13 may be replaced by other pickups which are displaced in phase 90 about the axis or path of travel of the member I. For example, in Fig. 8 a pickup structure is disclosed which includes a continuous annular or rectangular perimetric portion Bl. The perimetric portion has four pole pieces 5m, 5H), 5lc and 51d projecting inwardly to establish a cenguided. The aligned pole pieces 51a and 510 have windings IIB thereabout which are connected in series to replace the pickup coil Nb of 'Fig. 3. The remaining pole pieces have windings 8 r I 33 connected in series to replace the pickup coil" 13b of Fig. 3. In order to permit passage of knots or splices in the member I, two of the pole pieces 5la and 5'l'b may be made shorter than the re-. maining pole pieces. It will be understood that the pole ieces and the perimetric portion 5| all are constructed of a soft magnetic material such as soft iron.

Although the invention has been described with reference to certain specific embodiments tuerecr nuinrcus modifications falling within the spirit and scope of the invention are possible.

I elaiiii as my invehtioni I 1. In a system for reproducing an alternating signal havin maximum arid minimum fiequeiF cis which define a frequency range from an elorigated niagiietid movable member which transversuy maghetizable along its length to thereby produce a recor'ding' in accordance with the signal, nieans ifor'guidirig' the magnetic rawable member inthe direction or its length along a predete rr'riiried path, said member being subject to rotational movement while influenced by said guiding means, a pair of pickup elements adjacent a predetermined point on the path, said pickup elements being angularly spaced about the path to pickup signal components which vary in magnitude as a function of the rotational orientation of the transverse magnetization of the member, and which have frequencies sub= stantially' equal to the signal frequencies, and combining means having terminals for receiving two inputs, said combining means including phase-shifting means for shifting the phase of one of the inputs relative to the other of the inputs by an angle substantially equal to the angular spacing of the pickup elements, means including connections for supplying the two signal com: ponents respectively from said pickup elements as inputs to the combining means, said phase shifting means comprising a resistor connected to receive a first one of said inputs, a capacitor and a first coil connected in a series circuit for energization in accordance with a second one of said inputs, and a second coil mutually coupled to said first coil, translating means, and connections to said translating means for energizing the translating means in accordance with the voltage across said resistor, said capacitor and said second coil in series.

2. A system as claimed in claim 1, wherein the capacitance valve of said capacitor and the inductance valve introduced by said first coil are chosen to be substantially resonant at a frequency which is substantially the geometric mean of the frequency range represented by said maximum and minimum frequencies.

3. A system as claimed in claim 1, in combination with a second resistor, and a parallel resonant circuit connected through said second resistor across the first-named resistor, the capacitor and the second coil, said parallel resonant circuit being substantially resonant to the geometric mean of the frequency range represented by said maximum and minimum frequencies.

4. A system as claimed in claim 1, in combination with balancing means including resonant circuits for substantially balancing the impedances of the circuits energized by said inputs relative to said terminals for receiving the inputs.

5. A system as claimed in claim 1, wherein said series circuit includes a resistor in series with said capacitor and said first coil.

6. In a system for reproducing an alternating signal having maximum and minimum frequencies which define a frequency range from an elongated magnetic movable member which is adapted to be transversely magnetized along its length in accordance with said signal, means for guiding the magnetic movable member in the direction of its length along a predetermined path, said guiding means allowing rotational movement of said member, a pair of pickup elements adjacent a predetermined point on the path, said pickup elements being angularly spaced about the path to pick up respective signal components which vary in magnitude as a function of the rotational orientation of the transverse magnetization of the member, and which have frequencies substantially equal to the signal frequencies, and combining means having terminals for receiving first and second inputs, connections for supplying the two signal components respectively as said first and second inputs, said combining means including means for directly shifting the phase of said first input to produce a first output shifted in phase relative to the first input by an angle substantially equal to the angular spacing of the pickup elements, said second input providing a second output substantially in phase agreement with the second input, and adding means for adding said outputs to provide a resultant output having substantially the same frequencies as the inputs, and translating means responsive to the resultant output of said combining means, said frequency range being sufiicient in scope for the transmission of intelligible speech.

BERNARD E. LENEHAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,458,315 Sunstein Jan. 4, 1949 2,471,251 Tompkins May 24, 1949 2,476,110 Neufeld July 12, 1949 OTHER REFERENCES Journal of the Society of Motion Picture Engineers, November 1948, page 469. 

